The complement system is an important host defense system, however, inappropriate and/or excessive activation of the complement system has been implicated as contributing to the pathogenesis of many disease states, including post-cardiopulmonary bypass. There is evidence that the complement alternative pathway (AP) contributes significantly to the generation of pro-inflammatory agents in cardiac bypass. Complement activation products such as C3a, C5a, and sC5b-9 have been found within the blood of patients undergoing bypass and a positive correlation have been reported between the degree of complement activation and the post CPB complications. NovelMed has identified a potent inhibitor of the AP, which inhibits C3a, C5a, and C5b-9 in normal human serum. The focus of this study is to evaluate the effect of this inhibitor in an in vitro and ex vivo models of complement activation. In phase II this molecule will be converted into a clinical material and tested in a pediatric bypass circuit. NoveMed has filed a patent on the use of this inhibitor in cardiopulmonary bypass to inhibit alternative pathway activation. Rekha Bansal is a co-author of a patent "Process for inhibiting complement activation via the alternative pathway ", US patent 6,333,034, issued December 25, 2001